introduction to human anatomy - nervous system part 2

Autonomic Nervous System
The autonomic nervous system is the part of the nervous system
concerned with the innervation of involuntary structures
such as the heart, smooth muscle, and glands throughout the
body and is distributed throughout the central and peripheral
nervous system. The autonomic system may be divided into
two parts—the sympathetic and the parasympathetic—and
both parts have afferent and efferent nerve fibers.
The activities of the sympathetic part of the autonomic
system prepare the body for an emergency. It accelerates
the heart rate, causes constriction of the peripheral blood

vessels, and raises the blood pressure. The sympathetic part
of the autonomic system brings about a redistribution of
the blood so that it leaves the areas of the skin and intestine
and becomes available to the brain, heart, and skeletal muscle.
At the same time, it inhibits peristalsis of the intestinal
tract and closes the sphincters.
The activities of the parasympathetic part of the autonomic
system aim at conserving and restoring energy. They
slow the heart rate, increase peristalsis of the intestine and
glandular activity, and open the sphincters.